Grass control management in 2-gene Clearfield wheat

Friday

Nov 8, 2013 at 12:01 AM

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DallasPeterson K-State Weed Management Specialist dpeterso@ksu.edu

There arenow several 2-gene Clearfield wheat varieties onthe market: AP503 CL2 from Syngenta/AgriPro, Brawl CL Plus from Colorado StateUniversity, Doublestop CL Plus from Oklahoma State University,and WB-Deuce CL Plus from Monsanto/WestBred. More such varieties will no doubtbe on the market in the coming years.

What is thedifference between these varieties and the original 1-gene Clearfield varieties in terms of how they canbe managed, herbicide applications, grass control, and crop injury?

There is nodifference in the labeled rates of Beyond that can be applied in a singlegrowing season to 1-gene and 2-gene Clearfieldvarieties. However, methylated seed oil (MSO) or crop oil concentrate (COC) canbe added as an adjuvant to Beyond when it is used on 2-gene Clearfield varieties. On 1-gene Clearfield varieties, only a non-ionic surfactant (NIS) can be used as anadjuvant. In cases, a nitrogen-based fertilizer such as AMS or 28 percent UANshould also be added to the spray solution.

The adjuvantcan make a significant difference in the level of feral rye and downy bromecontrol with Beyond, especially with spring treatments. Since cheat, Japanesebrome, and jointed goatgrass are usually quite susceptible to Beyond, theadjuvant usually does not make as much difference in the level of control ofthese grasses. A recent K-State study near Manhattan illustrates the effect.

Note: The maximum single application use rate ofBeyond is 6 oz/acre. The 12 oz/acre rate would simulate spray overlaps in thefield and is not a labeled broadcast application rate.

For springapplications of Beyond, including MSO as an adjuvant measurably improvedcontrol of downy brome and feral rye compared to using NIS as the adjuvant. But as mentioned above,Beyond with MSO can only be used on 2-gene Clearfield varieties. MSO has been moreeffective than COC in these situations.

Beyond islabeled for control of many winter annual grasses (including jointed goatgrass,cheat, downy brome, and Japanese brome), but only suppression of feral rye.Control of feral rye with Beyond in K-State tests has been somewhat erratic andunpredictable. The best control will likely be achieved with fall applications,using the 6 oz rate instead of the 4 oz rate, and using MSO instead of NIS where that isallowed. In general, the best control of feral rye in 1-gene Clearfield varieties has been with fallapplications. With 2-gene Clearfieldvarieties, producers now have more options for better rye control.

The otheradvantage of 2-gene Clearfield over 1-gene Clearfield wheatvarieties is in the higher degree of crop safety from applications of Beyond.Occasionally, Beyond has caused some crop injury to 1-gene Clearfield wheat. This occurs most oftenwhere there is spray overlap (2x rates), when stress conditions prevail, orwhere wheat was not at the recommended treatment stages at the time ofapplication. In K-State tests, 2-gene Clearfieldwheat varieties have demonstrated much less potential for crop injury than1-gene varieties in these situations.